The present invention relates to environmental control systems for aircraft and enclosed spaces having an associated power source. More particularly, the invention details an advanced environmental control system which provides conditioned, pressurized air to an aircraft as well as liquid cooling for the avionics of the aircraft.
In order to operate at high altitudes, and corresponding low ambient temperatures and pressures, aircraft require a supply of conditioned, pressurized air for the cabin. In addition, the aircraft may require cooling for the assorted electrical and avionics systems. For certain applications, the avionic cooling load may be significantly greater than the cooling required for the cockpit and cabin.
Presently, the most common type of environmental control system is a bootstrap air cycle system. Examples of these types of systems are U.S. Pat. Nos. 4,198,830 and 4,580,406. The systems of these references seek to minimize the amount of bleed air required to power the air cycle system, while accommodating the entire cooling load.
Alternatively, vapor cycle systems have been used to provide cooling for the aircraft cabin and avionics. These systems require an additional supply of high-pressure air to pressurize the cabin and replace purged air. Within these systems, the high pressure air is usually supplied by an electrically driven or shaft driven compressor. However, since the electric power or shaft power must be supplied by the aircraft's engine, the efficiency losses associated with the compression operation make the system impractical. In order to solve this inefficiency problem, certain inventors have integrated bleed air systems with vapor cycle systems to efficiently provide conditioned, pressurized air and cooling for aircraft. An example of this type of system is U.S. Pat. No. 4,263,786.
However, an integrated system which efficiently utilizes bleed air to operate an air cycle system in combination with a vapor cycle system has heretofore not been available. Thus, the prior art systems requires large, bulky air conduits, significant amounts of electric power, and oversized heat transfer units. All of which combine to make the system heavy, inefficient and voluminous.
The present invention optimizes an integrated air cycle system and vapor cycle system resulting in an advanced environmental control system. The advanced system utilizes a minimum amount of bleed air, equivalent to the amount required to pressurize the cabin and replace purged or exhausted air. Potential energy within the bleed air is used to power both the air cycle system, and potentially the vapor cycle system. The advanced environmental control system provides maximum cooling capability while utilizing a minimum amount of bleed air within a compact, lightweight system which requires a reduced amount of ram air.